In the printing industry, it is sometimes necessary to process media multiple times in order to create a final product. For example, media such as paper may be pre-printed in an offset press, then run through a digital press/printer in order to add variable information. Examples of this type of printing include check printing, insurance policies, receipts, etc. Data printed on these forms is particularly important since the information is often used to guarantee traceability, facilitate record keeping, etc. In applications such as check printing, it is crucial that each individual document be readily identifiable and the correct number is printed in a proper location. Accordingly, it is desirable to quickly and easily verify defects in information printed on the medium.
Such printer defects are typically discovered using a print verification system (PVS). PVSs typically operate by digitizing printed pages using means such as photography, video, or scanning to generate test images. Subsequently, these test images are compared to source images that are known to be correct. The source images may be obtained from an input stream to be received at the printer, scanned after printing, or by a number of other methods.
However, current solutions to the problem of finding defects on pages outputted from a printer are limited in several ways. For instance, most approaches use a general pixel by pixel comparison. The drawback to such an approach is that no knowledge of individual objects on a page is used in the determination of whether or not a page is defective. Thus, there is an inability to identify incorrect placement of objects on a page.
Another limitation to current PVSs is a lack of a wider categorization of printed defects that includes a quality metric. For example, in some cases such as in the printing of Japanese Hiragana characters, pixel fidelity is required. However in other cases, such as in a jpeg compressed image, a more broad quality measure may be more appropriate.
Moreover, current PVSs assume that the system control unit is correct. Thus, there is no way to verify control unit errors. Also, generating application errors and operator errors (e.g., the wrong form being fed to the printer) cannot be detected in current PVS systems.
Accordingly, an improved printer verification mechanism is desired.